A display, a method for controlling the display, and a display system are provided. The method for controlling the display includes the following steps. analyzing an image after receiving image information to determine whether there is at least one object in the image; obtaining a block corresponding to each object in each of multiple frames of the image, and identifying object information in each block, wherein the object information includes an object type, reference point coordinates, and a frame time; obtaining a number of a target object according to the object type; calculating a moving speed of each target object according to the frame time and the reference point coordinates; and controlling brightness of a light source of the display according to the number and the moving speed. The disclosure can dynamically adjust the brightness of the light source according to different conditions.